The present invention relates to a copier, printer facsimile apparatus or similar image forming apparatus and more particularly to an operation unit including a readable screen for displaying various functions available with an image forming apparatus.
It is a common practice to arrange on, e.g., an electrophotographic machine an input device for allowing the operator to input various copying conditions as well as other conditions. The input device includes a print start key for starting a copying operation, a stop key for stopping it, numeral keys for inputting, e.g., a desired number of copies, and a magnification set key for setting a desired magnification.
Recent diffusion of microcomputers and extension of functions available therewith have implemented various kinds of copiers capable of executing various kinds of control with microcomputers. A microcomputer-controlled copier is capable of easily controlling a sophisticated copying process with a control program. Further, various functions including a function of displaying simple faults, e.g., the absence of papers and paper jams and a function of displaying the number of copies output have been added to the copier, making the most of the merits of a microcomputer. An advanced copier is capable of producing duplex copies each carrying images on both sides thereof, capable of sorting copies one by one, or capable of interrupting a copying operation under way, executing another copying operation, and resuming the previous copying operation after the completion of the interrupt copying operation. This kind of copier not only promotes convenient use, but also enhances efficiency.
Different keys are assigned to the above various functions while different information relating to the functions are displayed on a screen. The number of keys to be operated and the number of information to be displayed naturally increase with an increase in the number of functions available with the apparatus. It is, however, difficult to arrange all of the keys and screen in a limited flat area available on the top of the casing of the apparatus. Should the keys and screen be reduced in size in order to be accommodated in the limited area, they would be difficult to operate. Moreover, a number of keys arranged on the limited area would make the operation appear troublesome to perform. This is particularly true with a dual machine having a combined copier and facsimile function or a combined copier and printer function, and a multiplex machine having a combined copier facsimile and printer function.
In light of the above, there has recently been put to practical use an image forming apparatus including mechanical keys implementing only a start key, numeral keys and other basic keys and a touch panel implementing set keys and operation keys relating to various functions. The touch panel uses liquid crystal and selectively displays different key portions. Specifically, the apparatus displays information on a branched function step basis in order to make the screen readable, i.e., arrange function keys in a hierarchical fashion. In addition, icons and pop-up pictures as well as devised screen layout are used for reducing troublesome manipulation.
However, the problem with the touch panel scheme is that when the operator performing a sequence of setting steps desires to change any condition already set, the operator must sequentially switch the screen until a function step including the desired condition appears, and then change the condition. This operation is extremely troublesome to perform.